The present disclosure relates generally to communication systems, and more particularly, to cellular communications over unused unlicensed spectrum.
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
Recently, cellular communications such as LTE/LTE Advanced communications may be provided over unlicensed spectrum. However, such LTE/LTE Advanced communications may not share the medium efficiently with other unlicensed spectrum users such as wireless local area network (WLAN) devices. For example, Wi-Fi devices are already widespread in unlicensed spectrum, and therefore newly deployed LTE/LTE Advanced cells (e.g., small cells) need to coexist with the widespread Wi-Fi systems, and nearby Wi-Fi networks may need to be protected, especially when operating channels are generally occupied by Wi-Fi. Therefore, improvements in cellular communications over unlicensed spectrum are desired.